Field of Invention
The present relates generally to electrophotographic image forming devices, more particularly to polyimide fuser belts used in the heat fixing of toner in an electrophotographic printer. The polyimide fuser belts have increased thermal diffusivity without sacrificing mechanical strength when synthetic graphite or expanded synthetic graphite is used as a filler.
Description of Related Art
This invention relates to polyimide belts used in the heat fixing of toner in an electrophotographic printer. Such belts typically are moved across a heating element while in contact with paper or other media carrying toner to be fixed into such media by fusing. These types of belts, commonly referred to as fuser belts, must enable an electrophotographic printer to meet the demands of lower energy consumption, short time to first print and increased printing speed across a range of different media types.
A fuser belt used in an electrophotographic printer is required to have heat resistance, high thermal diffusivity, high wear resistance and strength with flexibility. A fuser belt is used in a fusing system in an electrophotographic printer to permanently fix or fuse the toned image onto the paper. Fusing of toner on paper is done by means of heat and pressure. This fixing process results in toner that is not easily removed from the paper. Prior to fusing, the toner is loosely bound to the paper and can be easily disturbed or rubbed off.
In belt fusers, toner is fused using a seamless, endless belt which is moved across a ceramic heater. The fuser belt and a backup member (such as a backup roller) act together to form a nip when pressure is applied.
A sheet carrying loose toner in the form of an image is pressed against the belt and heat transmitted by the belt fuses the toner into or onto the sheet. When the substrate carrying the toner passes through this nip, heat from the heated element and pressure within the nip fuse the toner onto the media.
The major process conditions affecting the fuse grade are belt surface temperature, nip time and nip pressure. The nip time is the residence time of the media in the nip. This is controlled by the rotational speeds of the rollers and the nip width. The nip width is determined by the pressure and elasticity of the rollers involved. The nip pressure is determined by the contact force between the rollers and the nip area. Higher temperature and longer nip time improves fuse grade. Increased pressure can also improve fuse grade.
The key print metrics of time to first print, print speed and energy consumption depend on the thickness of the fuser belt, the thermal diffusivity of the fuser belt and the power supplied to the heater. The most effective method of improving these print metrics is to increase the thermal diffusivity of the fuser belt. Accordingly, any method to increase the thermal diffusivity of the fuser belt used in an electrophotographic printer is desirable.